[819] in cryptography@c2.net mail archive
Proxy Cryptography draft available
daemon@ATHENA.MIT.EDU (Matt Blaze)
Tue May 13 19:01:29 1997
To: cryptography@c2.net
Date: Tue, 13 May 1997 18:37:10 -0400
From: Matt Blaze <mab@research.att.com>
I've put a draft of a new paper in my ftp directory. Comments and
discussion welcome. In particular, I'm curious if anyone can find
any real practical application for symmetric proxy functions.
ftp://ftp.research.att.com/dist/mab/proxy.ps
Proxy Cryptography
Matt Blaze
Martin Strauss
AT&T Labs -- Research
{mab,mstrauss}@research.att.com
Abstract:
This paper introduces {\em proxy cryptography,} in which a {\em
proxy function,} in conjunction with a public {\em proxy key,}
converts ciphertext (messages in a public key encryption scheme or
signatures in a digital signature scheme) for one key ($k_1$) into
ciphertext for another ($k_2$). Proxy keys, once generated, may
be made public and proxy functions applied in untrusted environments.
Various kinds of proxy functions might exist; {\em symmetric} proxy
functions assume that the holder of $k_2$ unconditionally trusts
the holder of $k_1$, while {\em asymmetric} proxy functions do not.
It is not clear whether proxy functions exist for any previous
public-key cryptosystems. Several new public-key cryptosystems
with symmetric proxy functions are described: an encryption scheme,
which is at least as secure as Diffie-Hellman, an identification
scheme, which is at least as secure as the discrete log, and a
signature scheme derived from the identification scheme via a hash
function.
